1. Field of the Invention
The present invention generally relates to a water content sensing and informing system for a disposable diaper. In its particular aspects, the present invention, relates to a water content sensing and informing system for a disposable diaper, that provides convenience and comfort to the person who wears it such as babies or bed ridden aged people, and instantly informs an individual when the diaper is substantially saturated and thus ready for changing.
2. Description of the Prior Art
Recently, the number of aged people has been increased owing to the progress of medical science, and also the number of bed ridden people has tended to increase simultaneously. In nursing homes for the elderly, it is estimated that at least 30 percent of the patients are bed riddens. In caring for such patients, the treatment of excrements has caused serious problems. It is obvious that providing a system for treating the excreation of urine would lessen the distress and burden for the patients and nursing home employees.
Conventionally, two systems have been commonly used for such urine treatment. The first is a diaper treatment using a diaper or napkins to absorb the excreted urine. The other is a continuous urine excretion treatment using an urethral catheter such as balloon catheter. The latter urine treatment system is continuously attached to the urinating organ of the patient.
The above mentioned diaper treatment will be discussed in detail as the present invention is related to this treatment. In hospitals or nursing homes, the time for changing diapers of the patients is fixed at certain intervals since the nurse has no way to know the urinating pattern of all of the patients. However, the systematic changing of patient's diapers at periodic intervals results in patients being left with a wet diaper for a long time causing discomfort and pain owing to a diaper rash, cooling, bed sores and the like.
In order to determine the individual urination pattern of patients, various methods to detect the water content in the diaper have been provided.
In our previous invention, Japanese Patent Application For Utility Model No. 57-165692, the present inventors have proposed a specific diaper comprising a water permeable inner sheet, a water impermeable outer sheet, a water absorber disposed between the inner and outer sheets and a water sensing means composed of a plurality of electroconductive metal layers or a stripe of electroconductive paper which is laminated on a paper or a plastic film.
Further, our previous invention Japanese Patent Application for Utility Model No. 58-202267, as shown in FIG. 7 and FIG. 8, discloses a modified example of the above diaper. The modified diaper comprises a plurality of metal layers (for convenience sake, two layers 2,2 are shown in these drawings) adhered to the surface of the water impermeable outer sheet 1 in order to detect the water content in the water absorber, not shown, by means of the change in electric conductivity between the two metal layers 2,2.
In addition to these inventions, the present inventors have provided a capacitor type water content detecting means as shown in FIG. 9 and FIG. 10 (Japanese Patent Application No. 59-128238 and No. 59-143649). Illustrated, in the figures, is a pair of metal thin layers 4 and 5 adhered to the surface of the water impermeable outer sheet 1. Layer 5 is covered with an insulating layer 6 so as to form the structure of a capacitor in this diaper. The electrostatic capacity of this capacitor corresponds to the amount of the water absorbed in the water absorber, not shown, of the diaper. The degree of wetness can be determined by detecting the change in the electrostatic capacity with well-known measuring devices. Accordingly, an information signal is generated only when the degree of wetness of the diaper reaches a predetermined level corresponding to the condition when the diaper should be changed. An AC voltage is applied to the capacitor, and the capacitor is connected to a compact oscillator, through lead wires, to transmit the information signal to a receiver located remote from the oscillator. This arrangement results in a significant increase in the consumption of electric power. Further, the capacitor type water content detecting system is extremely expensive to manufacture.
On the other hand, with the former device, which can detect the water content by monitoring the change in electric conductivity of electrodes, a diaper in the soiled state is readily detected by means of an electrical device. Therefore, the patients are spared any discomfort or pain. Although, this device can not determine the degree of wetness of the diaper, and the water detecting signal may be often generated even if the diaper is only slightly soiled. A small amount of water may be spread over a plurality of metal layers adhered on the same surface, so that the electric conductivity between the metal layers may change, and thus the water detecting signal may be transmitted. Further, an inadvertent signal may be generated owing to breakage or short-circuit between the metal layers as the patient or baby moves. These facts cause another problem in that the diapers are prematurely disposed. Nevertheless, this device does not require the lamination of the electric insulating layer on the metal layer, and thus its manufacturing process is not as complicated, and the consumption of electric power is lower than the above capacitor type water content detecting device.